1. Field of the Invention
The present invention generally relates to a vehicle information system operating method. More specifically, the present invention relates to a vehicle information system operating method that reliably determines fuel economy of the vehicle.
2. Background Information
Vehicles are increasingly providing useful data to drivers such as a distance-to-empty (DTE) reading. A DTE value is defined as simply an estimated distance that a vehicle can travel before running out of fuel. Typically, the DTE value is determined based on the current volume of fuel in the fuel tank as well as the fuel economy of the vehicle. Fuel economy is typically either a fixed value for a vehicle or determined based on fuel consumption during a recent period of time or over a set distance of travel. Typically, fixed values are considered to be highly unreliable for many reasons. For instance, subtle differences in fuel economy may exist even between vehicles of the same model. Also, a vehicle's fuel economy performance may change over time.
Although a running calculation of fuel economy can be more accurate than a fixed value, factors can also affect the reliability of this calculation. For example, once a vehicle is started, the vehicle consumes fuel whether or not the vehicle is moving. Therefore, significant swings and variations in the computed fuel economy can occur depending on whether fuel economy is updated at set time intervals or after set distances of travel. These variations can result in fluctuations in DTE value, which can cause driver confusion since one would not expect fuel economy to shift dramatically during a relatively modest period of vehicle operation.
One example of a vehicle information system is disclosed in U.S. Pat. No. 4,046,998, in which a vehicle information system determines an amount of fuel consumed during a specific time period based on a quantity of fuel processed by a fuel injection system, and then outputs a distance-to-empty value that was determined based on a current driving condition. Some other examples of vehicle information systems that output DTE readings are disclosed in the following U.S. publications: U.S. Pat. No. 4,157,030; U.S. Pat. No. 4,217,644; U.S. Pat. No. 4,400,779; U.S. Pat. No. 5,301,113; and U.S. Pat. No. 6,467,337.